Elevators are a crucial in getting many people back to the office — but experts say they could be coronavirus transmission hotspots

• The coronavirus typically spreads via droplets when an infected person is in close proximity to others.
• Viral particles can also live on surfaces like plastic and stainless steel for days.
• That makes elevators in apartment buildings and offices risky.
• Experts recommend increasing air flow in potentially crowded, indoor spaces to lower infection risk.

If you live in a sixth-story walk-up apartment, or your office is dozens of floors up in a high-rise, riding an elevator might be unavoidable.

But research suggests the coronavirus spreads best in places where people are within 6 feet of one another, and in poorly ventilated indoor spaces. This virus "really likes people being indoors in an enclosed space for prolonged periods of close face-to-face contact," William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University, previously told Business Insider.

That means elevators could be risky transmission hotspots. Linsey Marr, an aerosol scientist at Virginia Tech, told Business Insider that may be especially true "if they are crowded and people ride in them for a long time, like a minute or more several times a day."

Coronavirus particles can linger in the air

The coronavirus primarily spreads via droplets — particles larger than 5 micrometers — when an infected person coughs, sneezes, or speaks.

That's different than what scientists refer to as airborne transmission, which involves clouds of tiny viral particles known as aerosols (these are smaller than droplets) that linger in the air. An aerosolized form of a virus "means the drop doesn't go down right away; it hangs around for a bit," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said on a March episode of "The Daily Show."

"So you could come into a room thinking everything's all right, and then you inhale it," he added.

The measles virus can spread that way; it lives for up to two hours in an airspace where an infected person previously coughed or sneezed. The World Health Organization has said that's not the case for the coronavirus, yet several studies have identified live coronavirus particles in the air.

A study published last week found that talking loudly produces enough droplets to transmit the coronavirus to others, and that those droplets can linger in the air for at least eight minutes.

"There is a substantial probability that normal speaking causes airborne virus transmission in confined environments," the researchers wrote.

A study published in April also found live virus in the air in and around two hospitals in Wuhan, China. The highest concentrations were observed in confined areas with little air flow, such as in the air within the 9-square-foot toilet areas in patients' rooms, which were not ventilated. The amount of virus in the air in ventilated wards, however, was very low.

The Centers for Disease Control and Prevention, furthermore, says certain hospital procedures, like intubating a patient, "could generate infectious aerosols." A recent CDC study found that the coronavirus could travel up to 13 feet as an aerosol in hospital settings.

So it's possible that people who have COVID-19 — no matter whether they're presymptomatic, asymptomatic, or feeling ill — could leave some virus behind in stale elevator air.

"In such a tightly enclosed space without vigorous air movement for a short period of time, I'm afraid you might be exposed," Schaffner said.

Marr told NPR in April that "many elevators do not seem to have mechanical ventilation, like a fan, beyond the natural ventilation that occurs when the doors open and close."

Viral particles could survive for days on elevator buttons

The number of people in a given space and how close they get to each other matter most when it comes to coronavirus risk, according to Schaffner.

That applies to elevators, too: Marr thinks that "if you're riding by yourself, the risk is extremely low." But in a crowded office building, taking the elevator solo could be next to impossible.

Of course, there's also the issue of button pushing. A person can get the coronavirus if they touch a surface or object that has viral particles on it and then touch their mouth, nose, or eyes.

Although the coronavirus's lifespan on different surfaces depends on the surrounding temperature, humidity, type of surface, and other factors, two studies found that it lasts longest on stainless steel and plastic. One study found that the coronavirus lasted up to seven days on those surfaces, which are common in elevators. Another found that viral particles lived between two and three days on stainless steel and polypropylene, a type of plastic used in everything from toys to car parts.

So elevator buttons and doors could harbor viral particles for days.

Marr said it's important to "punch the buttons with something other than your fingers." If you have to touch them, wash or sanitize your hands.